The present invention provides techniques for tracking objects in sports programs and for selecting an appropriate camera view. The C-V converter unit includes an operational amplifier, a feedback capacitor, switching means connected in parallel with said feedback capacitor, a reference voltage-generating circuit for applying a reference voltage to the operational amplifier, and a drive voltage-generating circuit for applying a drive voltage to said sensor unit. The method includes monitoring a magnitude of the supply voltage and adjusting the refresh time as a function of the monitored magnitude of the supply voltage. The lower reduction rate decreases against the accelerator opening closer to a center opening.